1. Field of the Invention
The present invention relates to a transmission for a vehicle including a main shaft to which power from an engine is adapted to be transmitted, a counter shaft connected to a drive wheel, a plurality of gear trains respectively corresponding to a plurality of shift positions and provided between the main shaft and the counter shaft so as to be selectively established, a shifter relatively nonrotatably and slidably supported to the main shaft or the counter shaft to change the established condition of the gear trains, a shift fork for rotatably retaining the shifter, a shift drum having a lead groove on the outer circumference for engaging the shift fork, a shift drum center rotating with the shift drum, and a feed mechanism having a shifting motor for rotationally driving the shift drum center by a predetermined angle according to the operation of the shifting motor, wherein in sliding the shifter to change the established condition of the gear trains, the transmission of power from the engine to the main shaft is cut off.
2. Description of Background Art
Conventionally known in Japanese Patent Laid-open No. Hei 9-317881 is a transmission for a vehicle such that a plurality of positioning notches are formed on the outer circumference of a shift drum center rotating with a shift drum so as to be spaced at equal intervals in the circumferential direction of the shift drum center, wherein the shift drum center is intermittently rotated by a predetermined angle corresponding to the space between the adjacent positioning notches, thereby changing the established condition of a plurality of gear trains.
In the transmission disclosed in Japanese Patent Laid-open No. Hei 9-317881, the shift drum center is rotated at a fixed speed in changing the established condition of the gear trains. Accordingly, in sliding a shifter to change the established condition of the gear trains, a difference in speed between the shifter and a gear to be engaged with the shifter is relatively large, causing an increase in engagement noise. Particularly in such a vehicle that a shift position is automatically changed according to an upshift or downshift operation and that preliminary shifting is performed during running at any shift position, there is a possibility that a large engagement noise may be produced not in concert with the operation by an operator, so that the operator may feel discomfort in shifting.
It is accordingly an object of the present invention to provide a transmission for a vehicle which can reduce the engagement noise in changing the established condition of the gear trains by sliding the shifter.